Inductor for heating elongated workpieces

ABSTRACT

An elongated workpiece having two separate cylindrical portions with different diameters is inductively heated by an inductor including two generally parallel elongated conductors extending the length of the workpiece and magnetically coupled to the separate cylindrical portions. A conductive loop is connected between the parallel conductors generally adjacent the intersection of the cylindrical portions, and the reactance of the loop is changed to control the heating of the smaller cylindrical portion.

United States Patent Seyfried et al.

[ 51 Mar. 14, 1972 [54] INDUCTOR FOR HEATING ELONGATED WORKPIECES [72] Inventors: Richard F. Seyfried, Parma Heights; Norbert R. Balzer, Parma, both of Ohio Park-Ohio Industries, Inc., Cleveland, Ohio [22] Filed: June8, 1970 [21] Appl.No.: 44,321

[73] Assignee:

52 us. Cl ..219/10.79

s 1 Int. Cl. ..H05b 9/02 [58] Field of Search ..219/10.79, 10.43

[56] References Cited 7 UNITED STATES PATENTS 2,597,237 5/1952 Friend ..219/1o.19 x

2,647,200 7/1953 Redmond ..2l9/l0.79X

2,790,883 4/ 1957 Williamson ..2 19/ 10.79 3,472,988 10/1969 Seulen et al... ....2l9/l0.79 X 3,483,346 12/1969 Seulen et a1... ....2l9/l0.79 X 3,522,405 8/1970 Seulen et al. ..2l9/l0.79

Primary ExaminerJ. V. Truhe Assistant Examiner-Hugh D. Jaeger Attorney-Meyer, Tilberry and Body [57] ABSTRACT An elongated workpiece having two separate cylindrical portions with different diameters is inductively heated by an inductor including two generally parallel elongated conductors extending the length of the workpiece and magnetically coupled to the separate cylindrical portions. A conductive loop is connected between the parallel conductors generally adjacent the intersection of the cylindrical portions, and the reactance of the loop is changed to control the heating, of the smaller cylindrical portion.

1 Claims, 6 Drawing Figures PAIENTEBMAR 14 I972 3, 649 798 60 FIG. 6

22 INVENTORS.

RICHARD F. SEYFRIED a lgl pRBERT R. BALZER x 32 l2 0 32b Maya/L, WM ZBaJ ATTORNEYS INDUCTOR FOR HEATING ELONGATED WORKPIECES The present invention relates to the art of induction heating and more particularly to an improved inductor for heating an elongated workpiece.

The present invention is particularly applicable to inductively heating an axle shaft having a small diameter terminal end, and it will be described with particular reference thereto; however, it will be appreciated that the invention has much broader application and may be used for inductively heating a large variety of elongated workpieces, especially where a por-' tion of the elongated workpiece must be heated to a different extent than the remainder of the workpiece.

Until recently, axle shafts of the typeused in the automotive field have been inductively heated by moving an encircling inductor progressively along the workpiece in a vertical direction. This inductor inductively heated the workpiece. Directly below the inductor, and movable therewith, was a quench unit which progressively quench-hardened successive portions of the axle shaft immediately after they were inductively heated. This general arrangement has been widely accepted; however, considerable work is now being devoted to the development and improvement of a different technique in inductively heating and quench-hardening an axle shaft. In accordance with this technique, there is provided an inductor having two generally parallel conductors extending the complete length of the axle shaft. The axle shaft is then rotated with respect to these parallel conductors for inductively heating the total surface of the axle shaft at the same time.

Although the use of a single inductor extending the complete length of the axle shaft has been successfully used, certain difficulties have resulted. If the axle shaft has a reduced end portion, as is often the case, there is difficulty in effecting proper heating of the reduced portion since the same current flow is experienced in the parallel conductors adjacent the smaller portion of the axle shaft as in the parallel conductors adjacent the larger portion of the axle shaft. In the prior arrangement for heating axle shafts using a progressively moved, encircling inductor, when the inductor was adjacent a reduced portion of the axle shaft, the heating effect of the inductor was changed to vary the heating at this particular portion. This cannot be done by a single inductor extending the total length of the workpiece because the inductor is not progressed along the length of the workpiece.

The present invention relates to an improvement in an apparatus including a single inductor having parallel conductors extending the complete length of the elongated workpiece, which inductor has means for changing the heating effect of the inductor adjacent portions of the elongated workpiece.

In accordance with the present invention, there is provided an inductor for heating an elongated workpiece which inductor includes a loop having two generally parallel conductors extending along the workpiece and means for varying the current flow in a portion of said parallel conductors.

This invention relates to an inductor for inductively heatingan elongated workpiece having a central axis, while the workpiece is being rotated. This inductor comprises two elongated generally parallel conductors extending parallel to the axis of the workpiece and spaced from the workpiece, two crossover conductors joining these parallel conductors at their respective ends and means for causing a high frequency current that flows through the conductors. In accordance with the present invention, there is provided means for forming a conductive path between the parallel conductors to divide the conductors, and thus the inductor, into first and second sections and means for selectively changing the reactance of the conductive path to vary the current flow in one section of the inductor. By varying the current flow in a section of the inductor, it is possible to change the heating effect of the inductor adjacent a reduced portion of the elongated workpiece.

, The primary object of the present invention is the provision of an inductor for inductively heating an elongated workpiece, which inductor has two generally parallel conductors extending the length of the workpiece and including means for varying the heating effect along the parallel conductors.

Another object of the present invention is the provision of an inductor for inductively heating an elongated workpiece, which inductor has'two generally parallel conductors extending the length of the workpiece and including means for varying the heating effect along the parallel conductors, by using a variable reactance conductive path electrically parallel to at least one of the parallel conductors.

Another object of the present invention is the provision of an inductor for inductively heating an elongated workpiece, which inductor has two generally parallel conductors extending the complete length of a workpiece and including a conductive loop between the parallel conductors and means for varying the reactance of the conductive loop to vary the heating effect along the parallel conductors.

These and other objects and advantages will become apparent from the following description used to illustrate a preferred embodiment of the invention as taken in connection with the accompanying drawings in which:

FIG. 1 is a plan view illustrating, somewhat schematically, the preferred embodiment of the present invention;

FIG. 2 is a side elevational view of the embodiment illustrated in FIG. 1;

FIG. 3 is a cross-sectional view taken generally along line 33 of FIG. 2;

FIGS. 4 and 5 are enlarged partial views illustrating certain operating characteristics of the preferred embodiment of the invention; and,

FIG. 6 is an enlarged partial view similar to FIGS. 4 and 5 and illustrating a modification of the preferred embodiment of the invention.

Referring now to the drawings wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and not for the purpose of limiting same, FIGS. 1-5 show an apparatus A for inductively heating an axle shaft B having a central axis X, an end flange 10, a larger cylindrical portion 12, and a smaller cylindrical portion 14. In accordance with the invention, the workpiece, shown as axle shaft B, is elongated which indicates that it has a length at least 10 times the diameter of the larger cylindrical portion 12.

The axle shaft is supported between'two centers 20, 22 and is rotated by an appropriate rotating means, schematically illustrated as means 24. An inductor C includes two generally parallel conductors 30, 32 having stepped-down portions 30a, 32a and transition portions 30b, 32b. Thus, the inductor C is divided into three sections. These conductors 30, 32 are defined asbeing generally parallel and extending the complete length of the workpiece to be heated; however, it is appreciated that they are not'exactly parallel in that the transition portions 30b, 32b are necessary to connect the steppeddown portions to the remainder of these conductors. This allows the major portion of the conductors 30; 32 to have aspacing a where the stepped-down portions have a smaller spacing b. The ends of the generally parallel conductors are connected by crossover conductors 34,36. Appropriate leads 40, 42 intersect the conductor 32 and connect the inductor onto appropriate supply of high frequency electrical current, schematically represented as generator 44. Of course, the

parallel conductor 32 must be broken to form an electrical path between the leads 40,42.

As so far explained, the workpiece B isrotated about axis X by the rotating means 24, and high frequency current is supplied to the inductor C for heating both portions 12, 14 of the workpiece by current flow through the parallel conductors 30, 32. With this arrangement, the same current flows in the stepped-down portions 30a, 32a. This can cause an overheat-- ing of the smaller axle shaft portion 14. The present invention is directed toward the structure for preventing overheating of the smaller axle shaft portion, and it will be described in detail hereinafter.

In accordance with the present invention, there is provided a means for varying the current flow in at least one of the stepped-down portions 30a, 32a. This can be accomplished by providing, in the general vicinity of the transition between the larger and smaller cylindrical portions of the workpiece, a conductive path connecting the parallel conductors 30, 32 and an appropriate means for adjusting the reactance of this conductive path so that the current flow within the steppeddown portions 30a, 32a is reduced as required. This changes the current flow in both conductor portions 30a, 32a when the reactance of the conductive path is varied. Of course, a conductive path could be provided in electrical parallel with only one of the portions 30a, 32a. Then variation of the reactance would change current flow only in one of the stepped-down portions. This would still change the heating effect in shaft portion 14.

Although a variety of structures could be used to accomplish this invention, in accordance with the preferred embodiment illustrated in FIGS. 1-5, there is provided a conductor 50 having arcuate portions 52, 54, parallel portions 56, 58 and a loop 60 defining a central opening 62. The conductor 50 is formed from a conductive material similar to the material forming the rest of the inductor C so that the current flowing through the inductor C can be divided at the conductor to reduce the amount of current flowing through the steppeddown portion of the inductor C. A variety of structures could be used for adjusting the reactance of the path defined by the conductor 50; however, in accordance with the preferred embodiment of the invention there is provided an insert 70 having a nonmagnetic section 70a and a magnetic section 70b. The nonmagnetic section may be formed from a copper base material, and the magnetic section may be formed from ferrous base material. An appropriate rod 72 operated by cylinder 74 is used to move the insert 70 with respect to the opening 62 within loop 60. In FIG. 2, the insert 70 is completely removed from the loop so that the insert may be thoroughly seen; however, this is not the normal operating position for this particular insert. FIGS. 4 and 5 show the two actual operating positions of the insert 70. In FIG. 4, the nonmagnetic portion 70a is within the opening 52. This provides a low reactance, or resistance, for the conductor 50 so so that a high current flows through the conductor 50. Consequently, a relatively low current flows through the stepped-down portions 30a, 320. This reduces the heating effect of the steppeddown portions. Referring now to FIG. 5, the cylinder 74 has shifted the insert 70 to a second position with the magnetic portion 70b within the opening 62. In this instance, the reactance of the conductive path formed by conductor 50 is substantially increased. This forces a larger current flow through the stepped-down portion of the inductor so that a relatively high heating effect is caused at the reduced cylindrical portion 14 of the axle shaft B.

In operation, the axle B is rotated and the insert 70 is in the position shown in FIG. 5. In this manner, both the larger cylindrical portion 12 and the smaller cylindrical portion 14 are heated with substantially the same current flow through the respective parallel conductors. After the reduced portion 14 is heated to the desired amount, the insert 70 is shifted into the position shown in FIG. 4. This causes a reduced reactance of the conductive loop formed by conductor 50 so that current now flows through the conductor at a higher level. This substantially reduces the current flow through the stepped-down portion of the inductor C. In this manner, overheating of the reduced portion is avoided without substantially affecting the heating of the larger cylindrical portion 12.

In accordance with one aspect of the invention, an appropriate timer 76 is employed for shifting the insert 70 from the position shown in FIG. 5 to the position shown in FIG. 4 after an appropriate, preset time has expired during the heating cycle. Of course, a variety of timing arrangements could be employed for this purpose. In addition the insert could be manually shifted to effect changes in the current flow through the stepped-down portion of the inductor. It is also possible to provide more than one different type of magnetic and/or nonmagnetic section for the insert to provide more than two separate adjustments. Another arrangement for obtaining more than two adjustments is shown in FIG. 2 wherein the third position of the insert 70 IS illustrated. In this position, the

insert is removed from the opening 62 so that the opening has now a central air core. This provides a reactance for the path defined by inductor 50 intermediate the reactance formed by the insert portions 70a, 70b.

Referring now to FIG. 6, a modification of the present invention is illustrated. In this embodiment, the means for forming a conductive path between the two parallel conductors is device D which is essentially the same as device D except for the insert. Insert 80 is formed from either a magnetic or a nonmagnetic material. It is supported upon a rod 82 movable by cylinder 84. If insert 80 is formed from a magnet material, the reactance of this conductive path is decreased by shifting the insert 80 into the opening 62. It is appreciated that various other combinations could be used for effecting change of the reactance through the conductive path defined by the conductor 50.

Having thus described our invention, we claim:

1. In an apparatus for inductively heating an elongated workpiece having an axis, a first cylindrical surface and a second cylindrical surface, said first surface having a larger diameter than said second surface, said apparatus comprising an inductor including two parallel conductors and crossover conductors adjacent each end of said parallel conductors; and means for causing a high frequency current to fiow in said conductors; said parallel conductors having a first section magnetically coupled to said first surface and a second section magnetically coupled to said second surface, the spacing of said conductors at said first section being greater than the spacing of said conductors at said second section, said first and second sections being connected at an intermediate section of said parallel conductors between said first and second sections, the improvement comprising: means including a single branch conductor for forming a conductive path between said parallel conductors generally at said intermediate section and means for changing the reactance of said branch conductor to reduce the heating effect of said second section. 

1. In an apparatus for inductively heating an elongated workpiece having an axis, a first cylindrical surface and a second cylindrical surface, said first surface having a larger diameter than said second surface, said apparatus comprising an inductor including two parallel conductors and crossover conductors adjacent each end of said parallel conductors; and means for causing a high frequency current to flow in said conductors; said parallel conductors having a first section magnetically coupled to said first surface and a second section magnetically coupled to said second surface, the spacing of said conductors at said first section being greater than the spacing of said conductors at said second section, said first and second sections being connected at an intermediate sectioN of said parallel conductors between said first and second sections, the improvement comprising: means including a single branch conductor for forming a conductive path between said parallel conductors generally at said intermediate section and means for changing the reactance of said branch conductor to reduce the heating effect of said second section. 